求证：双曲线x²-15 y²=15与椭圆x²÷25+y²÷9=1的焦点相同
问题描述：
求证：双曲线x²-15 y²=15与椭圆x²÷25+y²÷9=1的焦点相同
答
x^2/15 - y^2 = 1, a^2 = 15, b^2 = 1, c^2 = a^2 + b^2 = 16, c = 4
同样,椭圆的c^2 = 25-9 = 16, c = 4